"For single phase home customers, you run a single one of those phases along a street and attach center tapped transformers to it." True but there are a few va

"For single phase home customers, you run a single one of those phases along a street and attach center tapped transformers to it." True but there are a few variations. And you also have to remember that each of those single-phase lines runs back (at some point to a three phase transformer. One very important facet of creating the single-phase spurs is to make sure the load is reasonably balanced. Three phase 240 VAC is also cheaply converted to 120 VAC single phase in the same transformer by putting a center-tap into one side of the transformer's delta-connected coils. You will get 120 VAC from that center tap to either of the adjacent hot connections but you'd better not connect anything between the center-tap and the opposite hot connection!